Hydraulically expanding hollow rivet



y 31, 1951 H. A. LEBERT 2,562,724

' HYDRAULICALLY EXPANDING HOLLOW RIVET Filed April 2, 1943 Patented July31, 1951 UNiTED TATES PATENT OFFICE HYDRAULICALLY EXPANDING HOLLOW RIVETHerbert A. Lebert, Cheyenne, Wye assign'or to United Air Lines, Inc, acorporation or Delaware Application April 2, 1843, Serial No. 481,521

4 Claims. 1

This invention relates to rivets and methods of riveting, moreparticularly to methods of riveting employing an improved rivet capableof being set and secured entirely from one side of the structure beingriveted and wherein heating or hammering of the rivet is eliminated, andthe invention has for an object the provision of improved methods ofthis character.

It has heretofore been. proposed to apply rivets to the work and tofinally set andsecure the rivets while operating entirely from one sideof the structure being riveted, the necessity for such rivets andmethods of riveting arising from the fact that in many structures oneside of the work is relatively or completely inaccessible. In carryingbut such prior methods, however, hollow rivets have been employed andthe upsetting or expanding force has heretofore been applied either byresort to explosive forces, the hollow rivet being provided with acharge therein capable of being detonated, or by driving pins or similarexpanding tools into the hollow rivets having specially formedconstrictions or shoulders therein to be engaged and forced outwardly bythe pins. The use of explosives in operations of this character is ofcourse inherently dangerous and costly, and in addition explosiveoperations are dimcult to control. Such mechanical expedients as haveheretofore been proposed have not resulted in uniform setting andsecuring of the rivets With out recourse to skilled operators andcareful manipulation. Something is yet to be desired, therefore, inmethods and rivets of the above character, and it is accordingly afurther object of this invention to provide an improved methodofriveting wherein an externally applied and controlled fluid pressureis exerted on the interior of the rivet to cause radial expansion andsetting of the rivet.

In carrying out the invention in one form, a rivet is provided havingashank portion and an enlarged head on one end thereof, the head and theshank being provided with a substantially axial or longitudinallyextending bore which extends inwardly from the head end of the rivet andterminates short of the opposite end of the shank. The hollow rivet thusprovided is inserted in the suitable openings of the structure to beriveted, and the bore or similar internal chamber is substantiallyfilled with a pressure transmitting fluid medium which is preferably aliquid or a flowable plastic, substantially incompressible material, andpressure is then applied to such medium from an externallylocated and"controlled source so as to cause the shank portion of the rivet to beradially enlarged. The pressure exerted is of sufiicient magnitude toovercome the yield point of the metal employed to form the rivet, andconsequently the shank portion of the rivet which extends through thework is radially expanded into tight contact with the work and theportion of the shank which projects beyond the work is bulged outwardlyto form an inner or second head on the rivet.

In one embodiment of the invention the filling material utilized may bea plastic substance, such as paraffin, and a small, closely fitting pinor plunger may be inserted into the open end of the bore in the rivetand forced inwardly by externally applied pressure so as to causeexpansion of the rivet. In another embodiment of the invention, apressure gun having a nozzle resembling a hypodermic needle may beinserted into the bore of the rivet and hydraulic pressure applied insufficient force to cause the desired 'expansion and bulging of theshank. Where it is desired to close or conceal the open end of the boreafter the rivet has been expanded or set, the head of the rivet may beprovided with a small flange or rim surroundingthe open end of the bore,and this may later be deformed inwardly so as to substantially close andconceal theopen end of the bore.

For a more complete understanding of the invention, reference should nowbe had to the drawing in which: 7

Fig. 1 is a somewhat diagrammatic longitudinal sectional view oi oneform of rivet embodying the invention, showing the rivet located in thework before the setting or expanding operation has been performed; I

Fig. 2 is a similar view of the rivet and work shown in Fig. 1,illustrating the rivet-after it has been set or expanded;

Fig. 3 is a view similar to Fig. 2 but illustrating another method ofapplying the desired fluid pressure for expanding the rivet;

Fig. 4 is a fragmentary view illustrating a modified type of rivet whichmay be employed;

and

Fig. 5 is a similar fragmentary view showing the rivet of Fig. 4 in itsfinished form, illustrating the manner in which the hole or core in therivet may be substantially closed and concealed.

R'eferring'now to Figs. 1 and 2 of the drawing, the invention is shownas applied to a rivet l0 having a shankportion H and an enlarged head 12on one end of the shank portion. As shown, the rivet HE] is providedwith a substantially axial or longitudinally extending bore 13 which extends inwardly from the head-end of the rivet and terminates short ofthe opposite end so as to leave an end wall H of substantial thickness.Although the bore I3, which provides an interior chamber in the rivet,may be of any suitable diameter, a bore having a diameter equal tosubstantially one-third the diameter of the rivet shank has been foundto be suitable.

As indicated in Fig. 1, the bore I3 is partially filled with apressure-transmitting material l5, which may be of any desired characterso long as it is of a fiuidic nature and capable of flowing underpressure. The material 55 may, for example, be an incompressible oil ormay take the form of a plastic material such as paraffin or the like.Where it is desired to fill the bore at the time of manufacture of therivet, it is of course desirable to employ a, plastic material whichwill not flow except when subjected to pressure.

As shown in Fig. 1, the rivet Ill is inserted through suitable holes ina structure to be riveted, such for example as the aligned holesillustrated in the plates l6 and ll, and there will usually be a slightclearance between the shank portion of the rivet and the holes in theplates. In order to apply pressure to the interior of the bore orchamber l3, any suitable means may be employed and in Fig. 1 this meansis illustrated as comprising a closely fitting pin or tool l8 which isinserted in the open end of the bore l3 1 so as to engage the fillingmaterial I5.

When the pin i8 is driven inwardly from the 'position shown in Fig. 1 tothe position shown in Fig. 2, for example, pressure will of course beexerted on the interior of the rivet shank and consequently the portionof the shank H which extends through the plates l6 and I1 will beradially enlarged or expanded so as to provide a tight fit between therivet and the plates. At

the same time, the projecting portion of the shank, since it isunsupported externally, will be bulged outwardly as shown in Fig. 2, soas to provide a head portion 19 on the inner end of the rivet. It willthus be seen that by this improved method of expanding the rivet a tightfit within the material being riveted is provided, and the manner inwhich the expanded head is formed insures that the rivet will be drawntightly into the work so that the originally formed head l2 tightlyengages the adjacent surface of the plate l8. Furthermore,

there is less possibility of modifying the grain structure of the rivetso as to cause crystallization, as may happen when the rivet is drivenby impact, and the well known hour glass form, which may be produced bythe application of impact forces on opposite ends of the rivet, isavoided.

Any convenient means for driving the pin l8 may of course be employed,such for example as air operated or electrically operated hammers, or ifdesired the pin may be driven by hand, utilizing sharp light hammerblows. Of course, the pin 18 may be provided, if desired, with suitablemeans to limit the extent to which it can be driven into the rivet, andsuch means are particularly useful where the pin l8 itself constitutesthe hammer element of an automatic hammer, since the pressure thusexerted on the interior of the rivet may in this fashion be accuratelypredetermined and controlled.

In Fig. 3 another method of expanding or setting the rivet isillustrated, the means there employed for exerting an externally appliedand controlled pressure being a suitable pressure gun' 2| having anozzle 22 which is in the form of a hypodermic needle, and which may beinserted into the open end of a suitable bore l3a in a rivet Illa. Inthis embodiment of the invention, the bore or chamber l3a is notnecessarily previously filled with a pressure-transmitting material, butthis material may be supplied directly from the pressure gun 2| duringthe expanding or setting operation. The expanding force here utilizedmay of course be exerted by any fluid medium capable of being suppliedunder pressure from conventional pressure guns. While hydraulic mediumsare preferably employed, the invention is of course not limited thereto.

In the rivet Illa illustrated in Fig. 3, the bore or chamber l3a may ofcourse be of any desired diameter, and the nozzle or needle 22 is of adiameter to provide a relatively close fit so that upon the applicationof a pressure medium through the nozzle 22 the projecting end of therivet will be expanded or radially enlarged to form a suitable head l9a.

In Fig. 4 a modified type of rivet is illustrated having a shank portion23 and a head portion 24, the head and the shank being provided with alongitudinal bore 25 similar to the bore l3 of Fig. l. The head 24 ofthe rivet is provided, as shown, with a suitable flange or rim 26surrounding the open end of the bore.

After the rivet has been expanded or set by means of an externallyapplied and controlled fiuid pressure exerted within the bore 25, thepressure-exerting means, such, for example, as the pin [8, may bewithdrawn and the flange or rim 25 may then be smashed or crushedinwardly so as to substantially close and conceal the outer end of thebore 25, as illustrated in Fig. 5. In some cases it may be desirable toretain the pressure-applying pin inside the rivet shaft as a means ofincreasing the shear strength. In such cases the length of the pin maybe so proportioned that it is driven to a position just flush with thesurface of the rivet head, where it may be retained, for added strength,by peening of the flange or rim 26.

While I have shown particular embodiments of my invention, it will beunderstood, of course, that I do not wish to be limited thereto sincemany modifications may be made, and I therefore contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of my invention.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. The method of riveting plates or the like together, which consists inproviding contiguous substantially aligned openings therethrough,inserting in said openings a rivet of material capable of acquiring apermanent set, said rivet having a head and a shank and a chamberextending axially from said head to a point near the end of the shank,the chamber in said shank extending beyond said plates a sufficientdistance to permit the bulging of the side wall of said chamber into ahead, and hydraulically expanding said shank laterally into snugengagement with the walls of said openings and upsetting said exposedshank end against a plate to form said head by introducing a fluid intosaid chamber and subjecting it to sufficient pressure applied in aseries of successive hammer-like impacts.

2. The method of riveting plates or the like together, which consists inproviding contiguous substantially aligned openings therethrough,inserting in said openings a rivet of material capable of acquiring apermanent set, said rivet having a head and a shank and a chamberextending axially from said head to a point near the end of the shank,the chamber in said shank extending beyond said plates a suflicientdistance to permit the bulging of the side wall of said chamber into ahead, and hydraulically expanding said shank laterally into snugengagement with the walls of said openings and upsetting said exposedshank end against a plate to form said head by introducing anincompressible fluid into said chamber and subjecting it to sufficientpressure applied in a series of successive hammer-like impacts.

3. A method of fastening together a plurality of contiguous memberscharacterized by the use of a hollow rivet, said method including thesteps of: entering the rivet through said members from one side of themembers so that it extends beyond said members; providing a mass ofsubstantially incompressible fluent material inside the rivet; insertinga pin into the rivet adapted to displace said mass of material byhydraulic action and thereby expand the rivet on the other side of saidmembers; and forcing said pin into said rivet by a series of successivehammer-like impacts.

4. A method of fastening together a plurality of contiguous memberscharacterized by the use of a hollow rivet, said method including thesteps of: entering the rivet through said mem bers from one side of themembers so that it extends beyond said members; providing a mass ofsubstantially incompressible fluent material inside the rivet; insertinga pin into the rivet adapted to displace said mass of material byhydraulic action and thereby expand the rivet on the other side of saidmembers; and forcing said pin into permanent position in said rivet by aseries of successive hammer-like impacts.

HERBERT A. LEBERT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,456,403 Ranney May 22, 19231,840,928 Anthony Jan. 12, 1932 1,945,480 Deems Jan. 30, 1933 2,162,164Febrey June 13, 1939 2,213,818 Krause Sept. 8, 1940 FOREIGN PATENTSNumber Country Date 689,584 Germany Mar. 28, 1940 705,153 Germany May 2,1941

